In a typical Code Division Multiple Access (CDMA) cellular network, such as a second generation (2G) CDMA communication network, transcoders are located in a radio access network (RAN), and in particular in a base station controller (BSC) located in the RAN. The transcoders receive compressed voice packets from a mobile station and convert the voice packets to pulse code modulated (PCM) signals for transmission through a circuit switched core network included in the cellular network. The BSCs then transmit the PCM signals upstream through the circuit switched core network and, via the core network, to a Public Switched Telephone Network (PSTN) coupled to the operator's cellular network. Similarly, PCM signals received by a 2G CDMA cellular network from a PSTN that are intended for a mobile station serviced by the RAN are transmitted as PCM signals through the circuit switched core network to the RAN, where the transcoder in the RAN converts the PCM signals to compressed voice packets. The RAN then transmits the compressed voice packets to the mobile station.
The development of next generation CDMA networks, such as a cdma2000 cellular network, have allowed system operators to install packet switched core networks in parallel with the circuit switched core networks, thereby permitting data packets to be transmitted through the cellular networks in parallel with circuit switched signals. The installation of such packet switched core networks permits a system operator to transmit voice data as a compressed voice packet through the packet switched core network, rather than transmit voice data as PCM signals through the circuit switched core network. To facilitate transmission of voice through a cellular network in a data packet format, operators of cdma2000 cellular networks have expressed an interest in relocating the transcoders closer to the PSTN. In addition, a relocation of transcoders to a more centralized location deeper in the cellular network can reduce system costs by providing a more centralized transcoder function, as opposed to a widely distributed, RAN-based, transcoder function, and by permitting voice services to be transported over more of a backhaul network in a compressed format as opposed to an uncompressed format.
However, when a legacy CDMA communication system is upgraded with a relocated transcoder function, a result may be a provision of a transcoding function in each of a core network and a RAN. Furthermore, some systems may service mobile stations that are not capable of transmitting voice in a format compatible for transmission over a packet switched core network, thus necessitating a transcoding function in a RAN. A result is that multiple transcoding functions may reside along a voice signal's path. The problem then arises as to which of the multiple transcoding functions shall encode/decode received voice.
Therefore, there exists a need for controlling where, in the cellular system, the transcoding function is performed, and what transcoding type(s) should be used in the serving network elements.